Many mechanisms for transporting toner (developer) by means of traveling-wave electric fields (as disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. S63-13074, Japanese Patent Publication (kokoku) No. H5-31146, and Japanese Patent Application Laid-Open (kokai) Nos. 2002-351218, 2003-15417, 2004-157259, 2005-275127, etc.) are conventionally known for use in image forming apparatus. In such a mechanism, a large number of strip-shaped electrodes are juxtaposed in a row on an electrically insulative substrate.
In such a mechanism, polyphase AC voltages are sequentially applied to the plurality of strip-shaped electrodes, whereby traveling-wave electric fields are generated. By the action of the traveling-wave electric fields, the above-described toner in a charged state is transported in a predetermined direction.